Comparison of midsagittal reference plane in PA cephalogram and 3D CT

Jin-Hyoung Cho; Ji-Yeon Moon

doi:10.4041/kjod.2010.40.1.6

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Comparison of midsagittal reference plane in PA cephalogram and 3D CT

Original Article

Korean J Orthod 2010;40(1):6-15.

Published online: 19 January 2010

DOI: https://doi.org/10.4041/kjod.2010.40.1.6

Comparison of midsagittal reference plane in PA cephalogram and 3D CT

Jin-Hyoung Cho, DDS, MSD, PhD^a, Ji-Yeon Moon, DDS, MSD^b

^aAssistant Professor, Department of Orthodontics, School of Dentistry, Wonkwang University.

^bGraduate Student, Department of Orthodontics, School of Dentistry, Wonkwang University.

Corresponding author: Jin-Hyoung Cho. Department of Orthodontics, Sanbon Dental Hospital, School of Dentistry, Wonkwang University, 1142, Sanbon-dong, Gunpo 435-040, Korea. +82 31 390 2896; e-mail, jjhdent@wonkwang.ac.kr.

Received 25 August 2009 Revised 4 December 2009 Accepted 9 December 2009

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Objective:

The aim of this study is to find the most helpful midsagittal reference plane for diagnosis in PA cephalometry compared with 3D CT.

Methods:

The subjects consisted of 25 adults who showed no facial asymmetry by gross inspection. 3D CT and posteroanterior cephalogram of the subjects were taken. To find the most helpful midsagittal reference plane in PA cephalometry, we considered five kinds of midsagittal planes from which the distances to five landmarks were measured and compared the result with that of 3D CT. The midsagittal plane for 3D CT was determined by the landmarks Nasion, Sella and Basion.

Results:

PA measurements using the midsagittal reference plane on a perpendicular plane lying through the midpoint of the right and left latero-orbitales was closest to those of 3D CT.

Conclusions:

It was considered that latero-orbitale perpendicular could be used as the helpful midsagittal reference plane to assess facial asymmetry in PA cephalometry.

Keywords: Three-dimensional computed tomography (3D CT), Posteroanterior cephalogram (PA), Midsagittal reference plane

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Fig 1.

Landmarks and midsagittal reference plane in 3D CT.

Fig 2.

Landmarks in posteroanterior cephalometric radiograph.

Fig 3.

Five kinds of midsagittal reference planes in posteroanterior cephalometric radiograph. A, Latero-orbitale perpendicular; B, zygoma perpendicular; C, Cg-ANS; D, foramen rotundum perpendicular; E, mastoidale perpendicular.

Table 1.

Landmarks used in this study

Landmark	Description
Nasion	The point of contact between frontal bone and suture between 2 halves of nasal bones
Sella	The midpoint of the pituitary fossa of sphenoid bone
Basion	The midpoint on the anterior margin of the foramen magnum
Cristagalli	The most superior point of crystal galli of the ethmoid bone
Anterior nasal spine	The tip of anterior nasal spine
Menton	The midpoint of the inferior border of mental protuberance
Upperincisor(Lt.,Rt.)	The midpoint on the incisal edge of the upper central incisor
Lowerincisor(Lt.,Rt.)	The midpoint on the incisal edge of the lower central incisor
Latero-orbitale(Lt.,Rt.)	The intersecting point between the external orbital contour laterally and the obliqueline
Jugularprocess(Lt.,Rt.)	The intersection of the maxillary tube rosity and zygomatic process of maxilla
Foramenrotundum(Lt.,Rt.)	The center of foramen rotundum
Zygoma(Lt.,Rt.)	The most lateral aspect of the zygomatic arch
Mastoidale(Lt.,Rt.)	The most inferior point on the mastoid process

Table 2.

Measurements of the distance of each landmark to the midsagittal reference plane in 3D CT and PA groups (unit: mm)

	CT		PA1		PA2		PA3		PA4		PA5
	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
ANS	0.032	0.622	−0.162	0.665	−0.326	0.770	0	0	−0.341	0.871	−0.210	1.113
Menton	−0.397	1.774	0.063	1.770	−0.334	1.772	0.077	2.856	−0.352	2.105	−0.087	2.403
Jugularprocess	0.083	1.243	0.472	1.039	0.064	1.188	0.728	0.971	0.172	1.461	0.294	1.915
Upperincisor	−0.281	3.073	0.370	3.093	−0.180	3.289	0.572	3.244	−0.230	3.906	0.338	4.368
Lowerincisor	−0.318	1.870	0.317	2.548	−0.220	2.724	0.411	3.028	−0.188	2.890	0.134	3.576

CT, 3DCT; PA1, PA using latero-orbital eperpendicular as midsagittal reference plane; PA2, PA using zygoma perpendicular as midsagittal reference plane; PA3, PA using Cg-ANS as midsagittal reference plane; PA4, PA using foramen rotundum perpendicular as midsagittal reference plane; PA5, PA using mastoidale perpendicular as midsagittal reference plane.

Table 3.

Comparison of differences between 3D CT and PA groups

	p value	Mean (mm)	Group	Duncan test^†
ANS	0.005^∗	0.415	│CT-PA1│	A
		0.552	│CT-PA2│	AB
		0.434	│CT-PA3│	A
		0.773	│CT-PA4│	B
		0.804	│CT-PA5│	B
Menton	0.023^∗	0.731	│CT-PA1│	A
		0.970	│CT-PA2│	BC
		1.631	│CT-PA3│	C
		1.098	│CT-PA4│	ABC
		1.460	│CT-PA5│	BC
Jugular	0.002^∗	0.742	│CT-PA1│	A
process		1.023	│CT-PA2│	AB
		1.414	│CT-PA3│	BC
		1.591	│CT-PA4│	BC
		1.760	│CT-PA5│	C
Upper	0.155	1.678	│CT-PA1│
incisor		2.194	│CT-PA2│
		2.272	│CT-PA3│
		2.091	│CT-PA4│
		2.881	│CT-PA5│
Lower	0.268	1.597	│CT-PA1│
incisor		1.823	│CT-PA2│
		2.207	│CT-PA3│
		1.681	│CT-PA4│
		2.386	│CT-PA5│

∗ p ＜ 0.05;

† Groups with samele t terare not different (p ＜ 0.05).

Table 4.

Pearson correlation coefficient between 3D CT and PA groups

		PA1	PA2	PA3	PA4	PA5
3DCT	ANS	0.741^†	0.683^†	NA	0.387	0.434
	Menton	0.830^†	0.698^†	0.685^†	0.711^†	0.659^†
	Jugularprocess	s 0.720^†	0.396	0.054	−0.037	0.120
	Upperincisor	0.793^†	0.589^†	0.674^†	0.741^†	0.579^†
	Lowerincisor	0.652^†	0.519^†	0.569^†	0.636^†	0.498^∗

∗ p ＜ 0.05;

† p <0.01; NA, not applicable.

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